1. Field of the Invention
The invention relates to a novel method for transferring and integrating endophytic fungi to non-host plants as heritable components.
2. Description of the Prior Art
In recent decades, the development of improved technologies for examining microscale communities of plant-associated fungi has contributed to increasing appreciation for the roles these organisms play in larger scale ecosystems. Using light and electron microscopy, chemical analysis, and molecular markers, it is now possible to detect and quantify the complex microbial communities inhabiting not only soils, but individual plants. For example, Vandenkoonhuyse et al. (2002, Evolution: Extensive Fungal Diversity in Plant Roots, Science, 295:2051-2051) used DNA sequence analysis to identify 49 species of fungi from the roots of a single grass plant, Arrhenatherum elatius. An even more complex community, consisting of 82 endophytic isolates, has been described in western white pine (Ganley et al., 2004, A community of unknown, endophytic fungi in western white pine, Proceedings of the National Academy of Sciences, 101:10107-10112). The majority of these microbes appear to be neither parasites nor simple decomposers (Ganley et al., ibid), and many exist symbiotically within host plants. Concrete demonstrations of microbial abilities to enhance plant growth by facilitating nutrient and water uptake (Hildebrandt et al., 2002, Expression of nitrate transporter genes in tomato colonized by an arbuscular mycorrhizal fungus, Physiologia Plantarum, 115:125), increasing biomass production, and modifying expression of chemicals involved in plant defense [Bultman and Bell, 2003, Interaction between fungal endophytes and environmental stressors influences plant resistance to insects, Oikos, 103:182-190; Mucciarelli et al., 2003, In vitro and in vivo peppermint (Mentha piperita) growth promotion by nonmycorrhizal fungal colonization, New Phytologist, 158:579-591] all suggest that microscale communities have significant potential to influence vegetative communities.
Some aspects of inoculating plants with symbiotic fungi are commonly practiced. For example, many crops are inoculated with mycorrhizal fungi that improve nutrient uptake and water use efficiency. Some legumes are regularly inoculated with nitrogen fixing bacteria to improve performance. Inoculation with fungal endophytes has also shown promise to protect plants from pathogens (Arnold et al., 2003, Fungal endophytes limit pathogen damage in a tropical tree, PNAS, 100:15649-15654).
Recently, Redman et al. (2002, Thermotolerance Generated by Plant/Fungal Symbiosis, Science, 298:1581) disclosed the isolation of a novel fungal endophyte, a Curvularia sp., from Dichanthelium lanuginosum plants collected from geothermal soils. This isolated fungal endophyte was then inoculated onto endophyte-free D. lanuginosum plants. The endophyte inoculated plants exhibited substantially greater heat tolerance than endophyte-free plants of the same species. In all of these cases, endophytes were first isolated from their native host prior to transfer to the recipient plant.